Vinyl polymers can be manufactured using suspension polymerization processes. In a typical suspension polymerization, a water-insoluble monomer or a mixture of water-insoluble monomers is dispersed in water and polymerized using an oil soluble initiator. Adequate agitation with desired flow patterns and suspending agents are utilized to maintain the stability of the suspension during the polymerization process. The polymerization reaction takes place in monomer droplets formed in the suspension, where the resulting product consists of a dispersion of polymeric particles in water. The polymeric particles can range from 20 micrometers (μm) to 4 millimeters (mm), where the particle size refers to the particle diameter as measured along a major axis.
For expandable polystyrene Manufacturing, the resulting product from the polymerization can then be screened to different size fractions based on pre-defined grade specifications and to separate fines and oversize particles.
The market demand for a particular grade varies by region and also from one season to another. A process capable of eliminating the waste fines (particles less than 0.4 mm) and oversize beads (particles greater than 2.5 mm) and/or that generates a narrower particle size distribution would be advantageous to keep up with market demands and in maintaining minimum inventory levels.